1. Field of the Invention
This invention relates to a compact wide-angle lens having a meniscus lens on the object side and a meniscus lens on the image side, which consists of five members and has a diaphragm between the third and fourth members.
2. Description of Related Art
Compact wide-angle lenses of this type are increasingly being used in the field of large-negative photography. Compared with conventional wide-angle lenses, they have shorter overall lengths, smaller lens diameters and a reduced weight. These advantages permit better utilisation of the adjustment options of a large-negative camera. The sensitivity to scale of compact wide-angle lenses is also less than that of conventional wide-angle lenses.
Compact wide-angle lenses are already known which comprise a dispersive meniscus lens both on the object side and on the image side.
DD WP 148 391 describes a wide-angle lens such as this, in which the central convergent lens part is constructed from four individual upright lens members. A meniscus lens with a cemented face is disposed in front of the diaphragm space in the direction of light. A disadvantage of this lens is that its unsymmetrical construction does not permit very large image angles.
Another compact wide-angle lens, which consists of six members with eight lenses, is claimed in EP 0 262 407. In this lens, the first lens member is constructed as a convex negative meniscus lens on the object side and the sixth lens member is of biconcave construction. This is claimed to result in a reduced overall length, and installation in cameras is improved due to the smaller lens diameter.
An approximately symmetrical wide-angle lens which is a double anastigmatic lens and which is described in DE OS 1 572 576 has a long overall length due to its eight lenses and is thus not a compact wide-angle lens in the actual sense of this term. Lenses of this type do in fact exhibit good sharpness and image field flatness, but do not permit high aperture numbers to be employed.
All these known compact wide-angle lenses are burdened with disadvantages. Thus troublesome chromatic aberrations, particularly colour defects, occur as magnifications become higher. Moreover, these compact wide-angle lenses do not enable such large image angles to be employed as those which are possible with conventional wide-angle lenses.
The aim of the present invention is therefore to create a compact wide-angle lens for which the said weaknesses of this type of lens do not arise.